Ethylene amines are used, inter alia, as solvents, stabilizers, for the synthesis of chelating agents synthetic resins, drugs, inhibitors and surface-active substances.
Ethylendiamine (EDA) and diethylenetriamine (bis(2-aminoethyl)amine; DETA) are used, in particular, as solvents for dyes and are starting materials for producing ion exchangers, pesticides, antioxidants, corrosion inhibitors, complexing agents, textile assistants and absorbents for (acidic) gases.
Numerous methods of preparing ethylene amines, in particular EDA and DETA, have been described in the literature.
Ethylene amines are produced, in particular, by means of two different technologies.
The amination of monoethanolamines by means of ammonia over transition metal catalysts gives a mixture of ethylenediamine (EDA), diethylenetetramine (DETA), aminoethylethanolamine (AEEA) and piperazine (PIP) and also small proportions of higher ethylene amines.
Amination of monoethanolamine (MEOA) by means of ammonia (cf., for example, PEP Report No. 138, “Alkyl Amines”, SRI International, Mar. 3, 1981 and U.S. Pat. No. 4,014,933 (BASF AG)) enables the formation of these higher ethylene amines (i.e. ethylene amines having a boiling point above that of triethylenetetramine (TETA)) to be largely suppressed in favor of ethylenediamine. However, aminoethylethanolamine (AEEA) and piperazine (PIP) are formed as by-products in this reaction.
The conversion of EDA into DETA over transition metal catalysts is known, for example, from GB-A-1,508,460 (BASF AG) and U.S. Pat. No. 4,568,746 (UCC)).
A second technology starts out from 1,2-dichloroethane (EDC) which is reacted with ammonia to form ethylene amines, with the hydrochlorides of the abovementioned ethylene amines being obtained first.
According to PEP Report No. 138, “Alkyl Amines”, SRI International, Mar. 3, 1981, in particular pages 7, 8, 13-16, 43-107, 113, 117, the reaction of dichloroethane with ammonia at molar ratios of 1:15 gives diethylenetriamine (DETA) with a proportion of ethylene amines formed of greater than 20% by weight. However, in addition to 40% by weight of ethylenediamine (EDA), 40% by weight of higher ethylene amines are obtained.
Furthermore, the hydrochlorides of the higher ethylene amines triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and pentaethylenehexamine (PEHA) are additionally formed. The reaction with ammonia to form the hydrochlorides is carried out in aqueous solution. The hydrochlorides are therefore obtained in solution and the amines are set free therefrom by addition of equimolar amounts of sodium hydroxide, i.e. an aqueous solution of the ethylene amines EDA (30-50% by weight), DETA (20-30% by weight), higher ethylene amines (30-40% by weight) and large amounts of sodium chloride is obtained as the crude product mixture. In the work-up of this mixture, all of the water is generally distilled off first. In a second step, all of the sodium chloride is then separated as a solid from the amines.
Disadvantages here are, in particular, the energy-intensive distillation of water and the removal of the sodium chloride (NaCl) as a solid.